1. Field of the Invention:
This invention relates to an air conditioner which supplies air with controlled specified temperature and humidity to a coating booth, and a method for conditioning the air thereby.
Generally the finishing quality of a coating in a coating booth highly depends upon the temperature and humidity of the air to be fed into the coating booth. Therefore, especially in the case of, for example, a body of an automobile or the like which is required to have a high quality for the paint coating, not only is dust in the air supplied to the coating booth eliminated, but the temperature and the humidity of the air are also strictly controlled within specific limits.
Accordingly, this invention relates to an improvement in the air conditioner for the coating booth for an automobile body or the like which requires a high quality for the coating thereof.
2. Description of the Prior Art:
In a conventional air conditioner for controlling the air to be supplied to a coating booth within predetermined temperature and humidity limits, dust in the air is first eliminated by a filter. The air is then transported past a heater to transmit heat to the air. Subsequently the air thus heated goes by articles, called "wet wall units", on the surfaces of which heated water is flowing down from the top to the bottom of the articles. The air is humidified due to the contact of the air with the heated water flow. Subsequently the air is again heated by passing through another plate fin coil heater within which steam flows.
In order to humidify the air to a predetermined humidity in the humidifying step, it is necessary to heat the water which flows down the wet walls to a predetermined temperature. Normally the heated water flowing down the surfaces of wet wall units is recirculated for energy-savings. Thus, a predetermined amount of the energy for heating the recirculating water is necessary for humidifying the air passing by. The smaller the ratio of recirculating water to air which passes by the wet walls, the higher the temperature of the recirculating water should be. However, since the recirculating water is heated in a recirculating water tank where the water is accumulated after flowing down the wet walls, there occurs a temperature difference for the heated water between the upper portion of the wet wall where the recirculating water starts flowing down and the lowermost portion of the wet wall. This temperature difference can become so large that to ensure the humidification of the air even at the lowermost portion of the wet walls, the initial temperature of the recirculating water must be so high that the air which passes through the upper portion of the wet wall is excessively humidified and reaches a supersaturated state. Thus, fog-like water droplets are produced in the air, and the temperature and humidity of the air cannot be sufficiently controlled. Further, water droplets will precipitate in a duct leading to the coating booth. Therefore, a large amount of recirculating water must normally be used for reducing the temperature difference between the upper portion and the lowermost portion of the wet walls from which the recirculating water starts flowing down. Therefore, according to this method, a large amount of energy is wasted for heating the large amount of water.